Internal-combustion engine



Feb. 27, 1945. A. 'FEROY INTERNAL-COMBUSTION ENGINE Filed March 18, 1944H-IS A INVENTOR A e ero i'wm 57 y;

Patented Feb. 21,-- 1945.

.v m-reo STATES PATENT OFFICE] 2,370,456 INTERNAL-COMBUSTION Enema ArneFeroy, New York, N. Y. Application March s, 1944, Serial No. 527,063

' 7 Claims;

This invention relates to internal combustion engines and its object isto provide a simple engine of low cost, capable of high specific Prformance.

The simplest engine is the two-stroke cycle with crankcase scavenging.It has no valves and no separate blower--no moving parts for pump or anyadditional parts or manufacturing cost.

The work needed for scavenging is less than with any engine having aseparate blower or scavenging pump. For example, to drive a rotaryblower may require about 17% of the engine power, which amount would.therefore not be available at the engine shaft. And of this powerrequired to drive the blower, only about half would actually move air,the other half being dissipated in mechanical and other'losses of theblower and its drive. Most rotary blowers have the "square indicatorcard, showing about twice the work needed to move the same air by apiston compressor. All things considered, the work done in .scavengingan engine by a. separate blower is about twice that done by crankcasescavenging.

The saving is available at the shaft of the I crankcase scavenged engineto increase its net output, and in manufacture, the cost of the separateblower is also saved.

One disadvantage of the crankcase scavenged engine has been itsinability to develop more than about 45 lbs/sq. in. BMEP. To get highspecific performance, it is necessary tohave-complete scavenging,requiring a volume of air about 140% of the piston displacement, but thecrankcase scavenged engine has only 100% of its piston displacement forpumping purposes, and with the losses usually present, it realizes onlyabout 70% of that. Consequently it gets about half the air it ought tohave for high performance. An object of this invention is to providemeans for increasing the air flow thru the engine to what it should befor high performance, without adding, complication to the engine. Inother words, an object is to make a simple crankcase scavenged enginesupercharge itself-to make the pumping action of the under side of thepiston put more air into theengine than the piston displacement.

In the drawing, Fi 1 is a transverse sectional view of an engineconstructed in accordance with the invention; Fig. 2 is a similar viewof a portion of the engine showing a modification of the structure; Fig.3 is a crankcase indicator diagram of an ordinary three-port engine; andFigs. 4 and 5 are crankcwe indicator diagrams of engines constructed inaccordance with the invention.

Referring to Fig. 1, the engine may be of wellknown three-porttwo-stroke type, comprising cylinder casting 6 closed at the top bycylinder head I and at, the bottom by oil pan 8. Piston I is operable inthe usual manner, being connected by connecting rod ii to, crankshaftl2.

Piston I0 is shown in top center position. Pis-. ton l0 may be said todivide the space between cylinder head i and oil pan 8 into twochambers, the cylinder or working chamber 8 above the piston, and thecrankcase or pumping chamber I9 below the piston.

Piston l0 overruns inlet ports i8, bypass ports 2!, and. exhaust ports22, in the usual manner, 20 well-known in three-port engines. Inletports l8 load from intake pipe H of considerable length.

Bypass ports 2! lead from bypass 20 connecting" pumping chamber IS withworking chamber 9.

Exhaust ports 22 lead out of working chamber 9 to exhaust pipe 28.

If more freedom is desired in controlling the tim of inlet ports intopumping chamber 58,

inlet pipe Ila, Fig. 2, may open directly thru ports Illa intdpumpingchamber l9, controlled by port IS in a rotating web member on cranmhaftE20,.

Operation of the engine on the two-stroke cycle, either Otto or Dieselcycle, is well understood. As a Diesel, piston M), on the upward strokecompresses a charge of airin working 35 chamber 9 sufiiciently to ignitethe fuel when injected, and the resulting combustion drives piston l0downward until ports 22 are opened,

- permitting the products of combustion to exhaust. I

This invention is concerned more with the pumping' action in chamber l9.

In Figs. 3, 4, and 5, S is the stroke of piston I0, and the dot-dashline A indicates atmospheric pressure. Heights of ports [8 and 2| aredenoted Hl8 and H2l respectively.

4 For comparison with the improvements of the invention, Fig. 3 showsthe pumping action in the crankcase of an ordinary three-port twostrokeengine (without pipe I! and with the ordinary short bypass connectingchambers I9 60 and 3 thru ports 2|, the bypass only just long enough toget around piston I, as usual). Piston If], on its upward stroke towardtop center in which it is shown, creates a depression in crankcasechamber I9 until ports l8 open, when II the depression is partiallysatisfied, but the preswhen ports l8 close.

around the piston thru a short bypass into working chamber 9. When ports2| are closed by piston ID, the pressure inpumping chamber I9 is stillabove atmospheric by the amount 32, so that piston It has to go furtherupward to reduce the pressure below atmospheric, to induce anothercharge of air to enter when ports |8 open again.

The pumping is inefficient at both ends of the stroke. The suctionstroke starts from a pressure above atmospheric, and the pressure strokestarts from a pressure below atmospheric.

Conditions at one end of the stroke can be improved by the addition of along enough inlet pipe l1. Fig. 4 shows pumping action in an engine withinlet pipe l1 and the ordinary short bypass connecting chambers l9 and 9thru ports 2|. Piston III, on its upward stroke toward top center,creates a depression in crankcase chamber I9, as before, until ports I8open, when air rushes in thru pipe |I, and the inertia of the column ofair in pipe I! forces more air into the crankcase, producing theoverpressure 4| Crankcase compression starts from above the atmosphericline A building up to higher pressure during the downward stroke ofpiston MI, so that when ports 2| open, more air flows into cylinder 9.And yet, because the bypass is short, there is still an overpressure 42in pumping chamber I9 when ports 2| close. Piston ID has to go part wayupward before pressure inchamber Is is reduced'to atmospheric. Thesuction stroke starts. inefficiently as before. Conditions have beenimproved at one end of the f pumpingstroke but not at the other.

, sion in crankcase |9..unti1 ports l8 open, when air rushes in'thrupipe l1 and ports I8, buildin up velocity in the column of air in pipeso 'that the inertia of the column forces more air into chamber l8,producing overpressure 5| when ports l8 close. Crankcase compressionstarts cific performance almost twice that usually possible withordinary crankcase scavenging.

While specific embodiments of the invention have beenshown and describedit is understood that changes may be made in the arrangement and in theconstruction of the various parts, without departing fromthe spirit orscope of the invention as expressed in the following claims.

I claim:

.1. ma two-stroke engine having a cylinder and a crankcase with a pistonoperable therebetween, a port opening into said crankcase, meansdelaying the opening of said port until said piston has nearly completedits upward stroke, and a conduit opening into said port from air at agiven pressure and so proportioned as to produce more than said givenpressure in said crankcase when said port closes.

2. In a two-stroke engine having a cylinder and a crankcase with apiston operable therebetween, a port opening into said crankcase,

means delaying the opening of said port until said piston has nearlycompleted its upward stroke, and a tubular passage opening into saidport from air at a given pressure such as atmospheric, said passagebeing long enough relative to the timing of said port to deliver moreair to said crankcase and to produce more than said given pressuretherein at the closing of said port.

3. Ina two-stroke enginehavin'g a cylinder and I a crankcase with apiston operable therebetween,

a port opening into said crankcase, means delaying the opening of saidport until said piston from above atmospheric pressure, building up ahigher pressure, so that when ports 2| open, more air flows intocylinder 9 thru long bypass 20, which in turn builds up velocity. Theinertia of the column of air in long-bypass 20 sucks more air out ofcrankcase l9, producing underpressure 52 therein by the time ports 2|close. .Thus when piston Ill starts upward on its suction stroke, thereis already less than atmospheric pressure in crankcase chamber l9.Consequently the de-. pression is greater than before, when ports l8open. The pumping efflciency is improved at both ends of the'stroke ofpiston l0, and its becomes possible to induce more air to flow thru thehas nearly completed its upward stroke, a conduit opening into said portfrom air at-a given pressure and so proportioned as to producemore thansaid given pressure in said crankcase when said port closes, a portopening into said cylinder from said crankcase when said piston. hasnearly completed its downward stroke, and means associated with saidlast-named port and producing less than atmosphericpressure in saidcrankcase when said last-named port closes.

4. In atwo-stroke engine-havinga cylinder and a crankcase with a pistonoperable therebe-. tween, a port opening into said crankcase,

means delaying the opening of said portuntil said piston has nearlycompleted its upward stroke, a 'pipe of such length leading to said portas to produce more than atmospheric pres-- sure in said crankcase whensaid port closes, a port opening into said cylinder when said piston hasnearly completed its downward stroke, and a pipe of such lengthconnecting said last-named port with said crankcase as to transfer moreair .from said crankcase to said cylinder and to reduce the pressure insaid crankcase to less than atmospheric when said last-named,portcloses.

5. A three-port two-stroke engine having 8. cylindex and a crankcasewith a piston operable therebetween, one port opening into saidcrankcase and uncovered by the lower edge of said piston when nearingtop center, a pipe'opening into said port, fromair at a given pressureand so proportioned as to produce more than said given pressure in saidcrankcase when said port closes,

a second port in said cylinder uncovered by the pper edge of said pistonwhen nearing bottom center, a bypass connecting said second port withsaid crankcase, and a third port in Said cylinder opening outwardly toexhaust said cylinder as said piston approaches bottom center.

6. A three-port two-stroke engine having a cylinder and a crankcase witha piston operable au os therebetween. one port opening into said crankcase and uncovered by the lower edge of said piston when nearink topcenter, a pipe of considerable length opening into said port; a secondport in said cylinder uncovered by the upper edge of said piston whennearing bottom center, a pipe of considerable length open1n8 into saidsecond port from said crankcase, and a third port in said cylinderopening outwardly to exhaust said cylinder as said piston approachesbottom center.

7. A three-port two-stroke engine having a cy'1-' inder and a crankcasewith a piston operable therebetween and three ports controlled by saidpiston, one opening into said crankcase; the

second openins into said cylinder from said crankcase, and thethirdopenins outwardly from said cylinder: the combination ot a 'pipe lead-AIR-NE FEROY.

